Twelve Somali men have been arrested during a terror probe in the Netherlands

Twelve Somali men have been detained in Rotterdam on suspicion of terrorist-related activities, the Dutch public prosecutor said.

The men, aged 19 to 48, were seized on Friday following a tip from the intelligence services that they were planning a terrorist attack shortly in the Netherlands. There was no immediate information on the alleged intended target.

European police often step up security around the festive season, but this year especially after a Nigerian man last Christmas Day taped explosives to his underwear and allegedly tried to blow up a plane as it approached Detroit.

There also have been growing concerns in Europe about festive season attacks following a suicide bombing in Sweden and attacks on two embassies this week in Rome.

Six of the Somalis live in Rotterdam, five have no permanent residence and one man comes from Denmark.

Last year, 24-year-old Omar Farouk Abdulmutallab, who had studied in London, boarded a Northwest Airlines flight to Detroit from Amsterdam. He is accused of trying to blow up the flight, and a judge in a court in Detroit has entered a not-guilty plea on his behalf.

Last Monday, 12 men were arrested in Britain in the largest counter-terrorism raid in nearly two years. The men - whose ages range from 17 to 28 - were arrested in London, Cardiff, Stoke-on-Trent and Birmingham. At least five were of Bangladeshi origin.

Security officials said a large-scale terror attack was aimed at British landmarks and public spaces. Lord Carlile, the Government's independent watchdog for terror, said the alleged plot appeared significant and involved several British cities, but he did not identify the targets.

Police removed computers from the suspects' homes. They have up to 28 days to either charge the men or release them. Possible targets that were scouted include the Houses of Parliament and shopping areas around the UK, according to a security official.

France, meanwhile, has ordered plain-clothes police patrols in key tourist sites for the festive season, including an extra 6,000 more police for New Year's Eve.